Road joints and method of producing same



April 3, 1934. J. w. HELTZEL ROAD JOINTS AND METHOD OF PRODUCING SAMEOriginal Filed March 11, 1926 face of the concrete.

Patented Apr. 3, 1934 'UNlTE STATES PATENT OFICE ROAD JOINTS AND METHODOF PRODUCING SAME 2 Claims. (Cl. 94-45) The present invention relates tothe building of concrete roads or other concrete surfacing structures,and the invention aims to provide a novel method of controlling thecreaking or fracturing of the concrete after it has set, and such methodmay also be used for making traffic lines and joints in concrete roadsor other surfacing structures.

As well known, roads and other surfacing structures composed of concretewill crack along irregular lines due to traffic or climatic changes, anda concrete road will usually become fractured along irregular lineslengthwise thereof due to the pressure and weight on the opposite sideportions of the road under heavy trafiic, and also due to the heavingaction of the ground or sub-base in freezing Weather. To overcome theirregular breaking of the concrete it has been the practice to installlongitudinal vertical division plates along the line where the break isdesired. These division plates are somewhat expensive, being embedded inthe concrete, and extending from the sub-base to a point close to or atthe sur- It has been a difficult problem to install such division platesalong a straight or regular line, and even with the use of such divisionplates an irregular break occurs, which, however, is not quite asobjectionable as a natural break.

With the foregoing objections in view, it is an object of the presentinvention to control. the

' heretofore.

low the surface of the concrete.

the concrete.

breaking of the concrete or to make a joint in the concrete which willbe less expensive and more effective than the use of division plates asWith those ends in View, division plates or strips are used which are ofless height than the division plates heretofore used, to provide foreconomy, and to space the upper edges of the division plates or stripsseveral inches be- These division plates or strips may also be installedmore quick ly, with a saving in cost, inasmuch as they need not beaccurately disposed on the sub-base. This obtains a saving both inmaterial and in installation, and, moreover, the division plates orstrips do not interfere with the tamping or finishing off of theconcrete above the division plates, as has occurred with the use of theordinary division plates that extend to or adjacent the surface of Theinvention consists further in forming a groove in the surface of theconcrete above the division plates or strips. This groove may be formedquickly and accurately, so as to After the concrete has hardened,

it will break between the groove and division plates or strips, saidgroove weakening the con crete above the division plates or strips sothat the concrete, in cracking, Will break along the line of the groove,which is the line of least re sistance in the fracturing of theconcrete. In this way, the breaking or fracturing of the concrete iscontrolled, for producing a joint in the concrete which may also serveas a traffic line for dividing oppositely moving trafic.

With the foregoing and other objects in view, which will be apparent asthe invention is more fully understood, the invention resides in themethod as hereinafter described and claimed, it being understood thatchanges may be made within the scope of what is claimed, withoutdeparting from the spirit of the invention.

The invention is illustrated in the accompanying drawing, wherein Figurel is a perspective view showing the several steps of the method employedand also illustrating the groove forming device in use.

Fig. 2 is a perspective view illustrating a modified form of divisionplate or strip.

Figs. 3 and 4 are cross-sections of completed joints showingmodifications in the division plates or strips.

Although the invention is described in connection with the building of aconcrete road, it will be understood that same may be used for otherconcrete surfacing structures for which the in- Vention is suitable.When building a concrete road the side forms or rails '7 are disposed onthe ground or sub-base to define the sides of longitudinal edges of theroad, and the grout is poured between said rails and the surface of theconcrete finished in any well known manner.

In carrying out the present invention to control the longitudinalbreaking of the concrete along the center line of the road, divisionplates or strips 8 are placed on the sub-base along the line where thelongitudinal break is desired. These strips 8 may be of thin sheetmetal, so as to be inexpensive, and need only be of a height of two orthree inches (more or less), so that their upper edges are spacedseveral inches below the surface of the concrete in the completed road.Such strips are therefore considerably cheaper than division platesheretofore used which extend from the sub-base to th upper surface ofthe concrete. It is unnecessary to locate the strips 8 along the desiredline with extreme accuracy, so as not to require painstaking care indisposing said strips on the sub-base, thereby saving time as comparedwith the installation of ordinary division plates. The strips 8 aresecured in place on the sub-base by means of stakes 9 driven into thesub-base, or other suitable means may be used for the purpose. Thestrips 8 have sockets 10 through which the stakes are driven. The strips8 may be plain, so as to be cheap, and may even be composed of wood,fibre, paper and other materials.

The positioning of the strips 8 on the sub-base is the first step of themethod and the next step consists in the pouring of the concrete on thesub-base between the rails 7 and over the strips. Said strips are placedon the sub-base in advance of the concrete mixer as it advances alongthe roadway. The concrete is struck off, tamped and finished in any ofthe well known methods, and the strips 8 being located several inchesbelow the surface of the concrete will not in any way interfere with thetamping and finishing of the concrete over said strips, which has causeddifficulty with the use of division plates extending close to thesurface of the concrete. The strips 8 are embedded in the lower portionof the concrete 11, thereby dividing the concrete at the bottom thereof.

The third step in the method consists in forming a groove or cut 12 inthe surface of the con crete above the strips 8. This groove 12 may beformed in the concrete while it is still plastic, and it is possible tomake the groove follow a definite straight or curved line, so as toproduce a neat and finished job. This groove not only provides a trairlcline along the center of the road for dividing oppositely movingtraffic, but also controls, in connection with the strips 8, thebreaking of the concrete after the concrete has set. The concrete willbreak along the weakened portion between the strips 8 and groove 12, andeven though the strips are not directly under the groove 12, the breakswill extend upwardly from said strips to the groove 12 due to theweakening of the con crete by said groove. As a result, the concretewill break accurately along the groove 12 although the breaks may beirregular below said groove. This irregular breaking of the concretebetween the groove 12 and strips 8 is even of advantage in locking theadjacent edges of the opposite slabs or sections together againstrelative vertical displacement. The strips 8 being cheaper in cost andless expensive to install as compared with the division platesheretofore used, will provide for economy, and the groove 12 may bequickly formed in the surface of the concrete. It is also apparent thatthe strips 8 may be di posed transversely of the concrete withtransverse grooves 12 above said strips, for producing transverse breaksor joints, and the strips and grooves may extend in different directionsin various concrete surfacing structures for controlling breaks andproducing joints.

The appliance shown in Fig. 1 for producing the groove 13 is disclosedin Patent No. 1,726,665 granted September 3, 1929, of which thisapplication is a division. Such appliance comprises a truck having thewheels 14 to move on one of the rails, and the truck has a bar 18carrying a trowel 20 provided with a longitudinal rib 24 to produce thegroove 12 in the surface of the concrete. Such appliance or any othersuitable device may be employed to produce the groove 12.

Fig. 2 illustrates a division plate or strip 8a having a plate 50riveted or otherwise secured to one side thereof at each end, and saidplates have the depending sharpened or pointed portions 51 to enter theground, thereby providing end stakes or pegs to enter the ground forholding the ends of the plate or strip in position. In order to hold theplate or strip 8a on the ground, a stake 9a is driven down into theground at one side of the strip and has a hook 52 at its upper end toengage over the upper edge of the strip.

Fig. 3 illustrates the use of a division plate or strip 81) which is ofcurved cross-section, and which is preferably supported above the groundor sub-base, so that when the concrete sets it will break between theupper edge of said strip and the groove 12, and between the lower edgeof said strip and the ground or sub-base, thereby forming the oppositeslabs or sections with an interlocking tongue and groove defined by thestrip 81). In order to support the strip 81), the stake 9b which isdriven into the ground may have an offset or seat 53 to support thestrip, said strip having apertures through which the upper terminal ofthe stake passes.

Fig. 4 illustrates the stake 92) used with the strip 8 which is fiat,for supporting the strip 8 above the ground.

Having thus described the invention, what is claimed as new is:-

1. The method of building a concrete road having a longitudinal joint,consisting in pouring the plastic concrete on a sub-base between sideform rails, embedding longitudinal dividing means in the plasticconcrete at a distance below the intended surface of the road, finishingthe surface of the concrete and allowing the concrete to set partially,and then moving a grooving tool, while guided from one of said rails,over the surface of the concrete above said dividing means to form agroove parallel with the corresponding side of the road and to determinethe line of breakage of the concrete between said dividing means and thesurface of the road.

2. The method of building a concrete road having a longitudinal joint,consisting in positioning division strips end to end above the sub-baseof the road at a distance below the intended surface of the road andlongitudinally of the road, pouring and finishing the concrete on saidsub-base over said strips between side form rails and permitting theconcrete to set partially, and then moving a grooving tool, while guidedfrom one of said rails, over the surface of the concrete ill) above saidstrips to form a groove parallel with JOSEPH WILLIAM HELTZEL.

